Wireless communication device

ABSTRACT

A wireless communication apparatus of the present invention has an interference signal cutoff circuit ( 10 ) for cutting off electric waves having interference frequencies of Δf=|frx±ftx| interposed between a receiving antenna ( 1 ) and a receiver ( 5 ). A transmitter ( 6 ) is connected to a transmitting antenna ( 11 ). 
     In this way, provision of the interference signal cutoff circuit ( 10 ) makes it possible to prevent degradation of reception characteristics, the degradation being caused such that the transmission wave radiated from the transmitter ( 6 ) and input to the receiver ( 5 ), mainly via the receiving antenna  1  is modulated with interference waves by active elements provided in the receiver ( 5 ) to generate interference waves having the same frequency as the reception frequency frx.

This application is the U.S. National phase of international applicationPCT/JP01/02800 filed on Mar. 30, 2001 which designates the U.S.PCT/JP01/02800 claims priority of JP Application No. 2000-94223 filedMar. 30, 2002.

TECHNICAL FIELD

The present invention relates to a wireless communication apparatus suchas a cellular phone, automobile phone and the like, for use in awireless communication system.

BACKGROUND ART

A conventional wireless communication apparatus such as a cellularphone, automobile phone and the like, for use in a wirelesscommunication system includes a receiving antenna 1 connected to areceiver 5 and a transmitting antenna 11 connected to a transmitter 6,as shown in FIG. 25.

In the thus configured wireless communication apparatus, the receptionsignal is received via antenna 1 and input to receiver 5 while atransmission signal is output from transmitter 6 and radiated externallyfrom antenna 11.

Generally, in most cases, the receiving antenna and transmitting antennaare integrated into one structure (designated at 1 in FIG. 26) and thesignal transmission path is branched by a duplexer (DUP) 4 into twopaths toward receiver 5 and toward a transmitter 6, as shown in FIG. 26.As another typical configuration, an active antenna changer switch 3 maybe used to perform switching between an external antenna terminal 7 andantenna 1, as shown in FIG. 27.

In a conventional wireless communication apparatus having theconfiguration as shown in FIG. 25, when an interference signalcorresponding to Δf=|frx±ftx| is input to antenna 1 where the receptionfrequency is represented as frx and transmission frequency isrepresented as ftx, jamming waves having a frequency equal to thereception frequency frx are generated by modulation between transmissionfrequency ftx and interference frequency Δf, in the active elementsincluded in receiver 5 or transmitter 6. Therefore, the wirelesscommunication apparatus has suffered the problem of its receptioncharacteristics being deteriorated by the jamming waves.

In a conventional wireless communication apparatus having aconfiguration shown in FIG. 26, the level of the signal of transmissionfrequency ftx entering from transmitter 6 to receiver 5 is markedlyhigh, so that the level of interference frequency Δf becomes furtherincreased. As a result, the wireless communication apparatus hassuffered the problem of its reception characteristics being furtherdegraded.

When an external antenna is used, an antenna changer switch is used asdisclosed in Japanese Patent Application Laid-open Hei 6 No. 37668. Inthe conventional wireless communication apparatus employing an activeantenna changer switch 3 as the antenna changer switch as shown in FIG.27, modulation between transmission frequency ftx and interferencefrequency Δf produces jamming waves having a frequency equal to thereception frequency frx. Accordingly, the wireless communicationapparatus has suffered the problem of its reception characteristicsbeing deteriorated by the jamming waves.

The present invention has been proposed in view of the above problems,it is therefore an object of the present invention to provide a wirelesscommunication apparatus which performs communication using the receptionand transmission frequencies, simultaneously, wherein degradation of itsreception characteristics due to interference signals is prevented.

DISCLOSURE OF INVENTION

In order to achieve the above object, the wireless communicationapparatus of the present invention has the following features.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously, is characterized in that an interference signal cutoffcircuit for cutting interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies is interposed between theinput terminal to a receiver and an antenna.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously, is characterized in that an interference signal cutoffcircuit for cutting interference signals having a frequency equal to thetransmission frequency is interposed between the input terminal to areceiver and an antenna.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously is characterized in that an interference signal cutoffcircuit for cutting interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies is interposed between theinput terminal to a transmitter and an antenna.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously and has a switch made up of active elements interposedbetween the input terminal to a receiver and an antenna, ischaracterized in that an interference signal cutoff circuit for cuttinginterference signals having frequencies approximately equal to theabsolute value of the sum or difference of the reception andtransmission frequencies is interposed between the switch and theantenna.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously and has a switch made up of active elements interposedbetween the input terminal to a receiver and an antenna is characterizedin that an interference signal cutoff circuit for cutting interferencesignals having frequencies approximately equal to the absolute value ofthe sum or difference of the reception and transmission frequencies isinterposed between the switch and the input terminal to the receiver.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously and has a switch made up of active elements interposedbetween the input terminal to a receiver and an antenna is characterizedin that interference signal cutoff circuits for cutting interferencesignals having frequencies approximately equal to the absolute value ofthe sum or difference of the reception and transmission frequencies areinterposed between the antenna and the switch and between the switch andthe input terminal to the receiver.

In the above-described wireless communication apparatus of the presentinvention, the interference signal cutoff circuit may be composed of atrap circuit having a resonance frequency approximately equal to theabsolute value of the sum or difference of the reception andtransmission frequencies.

Also, in the above-described wireless communication apparatus of thepresent invention, the interference signal cutoff circuit may becomposed of a bandpass filter having pass bands including thecommunication frequency and the transmission frequency and having anattenuation band around the frequency approximately equal to theabsolute value of the sum or difference of the reception andtransmission frequencies.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously and has a switch made up of active elements interposedbetween the input terminal to a receiver and an antenna is characterizedin that an impedance adjusting circuit for adjusting the impedance tointerference signals having frequencies approximately equal to theabsolute value of the sum or difference of the reception andtransmission frequencies is interposed between the switch and the inputterminal to the receiver.

In the above-described wireless communication apparatus of the presentinvention, 2110 Hz to 2170 Hz can be used for the reception frequencyand 1920 Hz to 1980 Hz can be used for the transmission frequency.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously is characterized in that a circuit presenting a lowimpedance to interference signals having frequencies approximately equalto the absolute value of the sum or difference of the reception andtransmission frequencies is provided as a part of an antenna.

In accordance with a wireless communication apparatus of the presentinvention, a wireless communication apparatus which establishescommunication using reception and transmission frequenciessimultaneously, is characterized in that a circuit which presents highimpedances at the reception frequency and the transmission frequency andwhich presents a low impedance to interference signals havingfrequencies approximately equal to the absolute value of the sum ordifference of the reception and transmission frequencies is provided asa part of an antenna.

As has been described above, since the wireless communication apparatusof the present invention includes an interference signal cutoff circuitfor cutting off interference signals which are originated fromtransmission reception frequencies when the reception and transmissionfrequencies are used simultaneously for communication, it is possible toimprove the reception characteristics.

Further, use of a specifically set up trap circuit as the interferencesignal cutoff circuit makes it easy, and possible, to achieve largeattenuation at frequencies at which cutoff is wanted.

Use of a specifically set up bandpass filter as the interference signalcutoff circuit prevents attenuation in the transmission and receptionfrequency bands.

Provision of an impedance adjusting circuit for adjusting the impedanceto interference signals makes it possible to markedly reduce the powerof received interference waves, hence improve the receptioncharacteristics.

As has been described above, since the wireless communication apparatusof the present invention includes an interference signal cutoff circuitfor cutting off interference signals which are originated fromtransmission reception frequencies when the reception and transmissionfrequencies are used simultaneously for communication, it is possible toimprove the reception characteristics.

Further, use of a specifically set up trap circuit as the interferencesignal cutoff circuit makes it easy, and possible, to achieve largeattenuation at frequencies at which cutoff is wanted.

Use of a specifically set up bandpass filter as the interference signalcutoff circuit prevents attenuation in the transmission and receptionfrequency bands.

Provision of an impedance adjusting circuit for adjusting the impedanceto interference signals makes it possible to markedly reduce the powerof received interference waves, hence improve the receptioncharacteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the first embodimentof the present invention;

FIG. 2 is a circuit diagram showing an example of an interference signalcutoff circuit;

FIG. 3 is a circuit diagram showing an example of an interference signalcutoff circuit;

FIG. 4 is a circuit diagram showing an example of an interference signalcutoff circuit;

FIG. 5 is a circuit diagram showing an example of an interference signalcutoff circuit;

FIG. 6 is an illustrative chart showing the simulation result forverifying the characteristics of an interference signal cutoff circuit,trap circuit and bandpass filter used in a wireless communicationapparatus according to the present invention;

FIG. 7 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the secondembodiment of the present invention;

FIG. 8 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the third embodimentof the present invention;

FIG. 9 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the fourthembodiment of the present invention;

FIG. 10 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the fifth embodimentof the present invention;

FIG. 11 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the sixth embodimentof the present invention;

FIG. 12 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the seventhembodiment of the present invention;

FIG. 13 is a circuit diagram showing an example of a trap circuit;

FIG. 14 is a circuit diagram showing an example of a trap circuit;

FIG. 15 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the eighthembodiment of the present invention;

FIG. 16 is a circuit diagram showing an example of a bandpass filter;

FIG. 17 is a circuit diagram showing an example of a bandpass filter;

FIG. 18 is a chart for illustrating an experimental result ofimprovement in error rate for verifying the effect of the wirelesscommunication in accordance with the eighth embodiment of the presentinvention;

FIG. 19 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the ninth embodimentof the present invention;

FIG. 20 is a chart for illustrating an experimental result ofimprovement in error rate for verifying the effect of the wirelesscommunication in accordance with the ninth embodiment of the presentinvention;

FIG. 21 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the first embodiment0 of the present invention;

FIG. 22 is a circuit diagram showing an example of a trap circuit;

FIG. 23 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the first embodiment1 of the present invention;

FIG. 24 is a circuit diagram showing an example of a bandpass filter;

FIG. 25 is a block diagram showing a schematic configuration of aconventional wireless communication apparatus;

FIG. 26 is a block diagram showing a schematic configuration of aconventional wireless communication apparatus with a common antennashared for transmission and reception; and

FIG. 27 is a block diagram showing a schematic configuration of aconventional wireless communication apparatus including an activeantenna changer switch.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the embodiments of wireless communication apparatus of the presentinvention will be described with reference to the drawings.

<The First Embodiment>

FIG. 1 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the first embodimentof the present invention.

As shown in FIG. 1, the wireless communication apparatus according tothe first embodiment of the present invention has an interference signalcutoff circuit 10 for cutting off electric waves having interferencefrequencies of Δf=|frx±ftx| interposed between a receiving antenna 1 anda receiver 5. A transmitter 6 is connected to a transmitting antenna 11.

Unless a wireless communication apparatus is provided with thisinterference signal cutoff circuit 10, the transmission wave radiatedfrom transmitter 6 and input to receiver 5, mainly via receiving antenna1, and interference waves are modulated by active elements provided inreceiver 5 to generate interference waves having the same frequency asthe reception frequency frx, causing degradation of receptioncharacteristics. In the wireless equipment of the first embodiment ofthe present invention, provision of interference signal cutoff circuit10 makes it possible to prevent such degradation of receptioncharacteristics.

[Interference Signal Cutoff Circuit]

Circuit examples of the above-described interference signal cutoffcircuit 10 are shown in FIGS. 2 to 5.

To begin with, description will be made of the case where theinterference frequency is in such relationship as Δf=|frx−ftx|.

The interference signal cutoff circuit 10 shown in FIG. 2 is made up ofan inductor L2 arranged in parallel with the main circuit. Since thisinterference signal cutoff circuit 10 presents a low impedance at thefrequency Δf and high impedances at the transmission frequency ftx andat the receiving frequency frx, interference waves of Δf can be cut off.

The interference signal cutoff circuit 10 shown in FIG. 3 is made up ofa capacitor C3 arranged in series with the main circuit. Since thisinterference signal cutoff circuit 10 presents a high impedance at thefrequency Δf and low impedances at the transmission frequency ftx and atthe receiving frequency frx, interference waves of Δf can be cut off.

Next, description will be made of the case where the interferencefrequency is in such relationship as Δf=|frx+ftx|.

The interference signal cutoff circuit 10 shown in FIG. 4 is made up ofan inductor L7 arranged in series with the main circuit. Since thisinterference signal cutoff circuit 10 presents a low impedance at thefrequency Δf and high impedances at the transmission frequency ftx andat the receiving frequency frx, interference waves of Δf can be cut off.

The interference signal cutoff circuit 10 shown in FIG. 5 is made up ofa capacitor C9 arranged in parallel with the main circuit. Since thisinterference signal cutoff circuit 10 presents a high impedance at thefrequency Δf and low impedances at the transmission frequency ftx and atthe receiving frequency frx, interference waves of Δf can be cut off.

FIG. 6 shows the simulation result for verifying the characteristics ofan interference signal cutoff circuit 10 used in the wirelesscommunication apparatus according to the first embodiment. In thissimulation, the interference signal cutoff circuit 10 having the circuitconfiguration shown in FIG. 2 was used. In FIG. 6, ‘Parallel L’indicated by the thin broken line represents the interference signalcutoff circuit 10 used in the wireless communication apparatus of thefirst embodiment.

Here, it is assumed that, for example, reception frequency frx=800 MHz,transmission frequency ftx=600 MHz and Δf=200 MHz. It is clearlyunderstood from the simulation result shown in FIG. 6 that insertion ofinterference signal cutoff circuit 10 attenuates Δf by about 8.5 dB. Theloss in the pass band range is about 2.5 dB at ftx and about 1.7 dB atfrx.

<The Second Embodiment>

FIG. 7 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the secondembodiment of the present invention.

As shown in FIG. 7, the wireless communication apparatus according tothe second embodiment of the present invention has an ftx cutoff circuit15 for cutting off electric waves of a transmission frequency ‘ftx’interposed between a receiving antenna 1 and a receiver 5. A transmitter6 is connected to a transmitting antenna 11.

Unless a wireless communication apparatus is provided with this ftxcutoff circuit 15, the transmission wave radiated from transmitter 6 andinput to receiver 5, mainly via receiving antenna 1, and the receivedwaves are modulated by active elements provided in receiver 5 togenerate interference waves having frequencies of Δf=|frx±ftx|. As aresult, the reception characteristics degrades if Δf is set as theintermediate frequency in reception. In the wireless equipment of thesecond embodiment of the present invention, provision of ftx cutoffcircuit 15 makes it possible to prevent such degradation of receptioncharacteristics.

The ftx cutoff circuit 15 may use the same circuit configurations (seeFIGS. 2 to 5) as the interference signal cutoff circuit 10 used in thewireless communication apparatus according to the first embodimentdescribed above. In this case, the cutoff frequency should be setbetween frx and ftx.

<The Third Embodiment>

FIG. 8 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the third embodimentof the present invention.

As shown in FIG. 8, the wireless communication apparatus according tothe third embodiment of the present invention has an interference signalcutoff circuit 10 for cutting off electric waves having interferencefrequencies of Δf=|frx±ftx| interposed between a receiving antenna 11and a transmitter 6. A receiver 5 is connected to a receiving antenna 1.

Unless a wireless communication apparatus is provided with thisinterference signal cutoff circuit 10, interference waves and thetransmission wave input to transmitter 6 are modulated by activeelements provided in transmitter 6 to generate interference waves havingthe same frequency as the reception frequency frx. The generatedelectric waves are input to receiver 5, causing degradation of receptioncharacteristics. In the wireless equipment of the third embodiment ofthe present invention, provision of interference signal cutoff circuit10 makes it possible to prevent such degradation of receptioncharacteristics.

The interference signal cutoff circuit 10 may use the same circuitconfigurations(see FIGS. 2 to 5) as the interference signal cutoffcircuit 10 used in the wireless communication apparatus according to thefirst embodiment described above.

<The Fourth Embodiment>

FIG. 9 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the ninth embodimentof the present invention.

In the wireless communication apparatus according to the fourthembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.9, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between antenna land an externalantenna terminal 7 is interposed between antenna 1 and duplexer 4. Aninterference signal cutoff circuit 10 for cutting off electric waveshaving interference frequencies of Δf=|frx±ftx| is interposed betweenantenna 1 and active antenna changer switch 3.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from duplexer 4between the signal path to interference signal cutoff circuit 10 andexternal antenna terminal 7.

Duplexer 4 outputs the high frequency reception output signal fromactive antenna changer switch 3 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to active antennachanger switch 3.

Unless a wireless communication apparatus is provided with thisinterference signal cutoff circuit 10, the transmission wave andinterference waves of interference frequencies Δf are modulated inactive antenna changer switch 3 to generate interference waves havingthe same frequency as the reception frequency frx, causing degradationof reception characteristics. In the wireless equipment of the fourthembodiment of the present invention, provision of interference signalcutoff circuit 10 makes it possible to prevent such degradation ofreception characteristics.

The interference signal cutoff circuit 10 may use the same circuitconfigurations(see FIGS. 2 to 5) as the interference signal cutoffcircuit 10 used in the wireless communication apparatus according to thefirst embodiment described above.

<The Fifth Embodiment>

FIG. 10 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the fifth embodimentof the present invention.

In the wireless communication apparatus according to the fifthembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.10, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between an external antennaterminal 7 and antenna 1 is interposed between antenna 1 and duplexer 4.An interference signal cutoff circuit 10 for cutting off electric waveshaving interference frequencies of Δf=|frx±ftx| is interposed betweenactive antenna changer switch 3 and duplexer 4.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from interferencesignal cutoff circuit 10 between the signal path to antenna 1 andexternal antenna terminal 7.

Duplexer 4 outputs the high frequency reception output signal frominterference signal cutoff circuit 10 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to interferencesignal cutoff circuit 10.

Unless a wireless communication apparatus is provided with thisinterference signal cutoff circuit 10, part of the waves of interferencefrequencies Δf and the transmission wave are modulated in activeelements provided in receiver 5 to generate interference waves havingthe same frequency as the reception frequency frx, causing degradationof reception characteristics. In the wireless equipment of the fifthembodiment of the present invention, provision of interference signalcutoff circuit 10 makes it possible to prevent such degradation ofreception characteristics.

The interference signal cutoff circuit 10 may use the same circuitconfigurations(see FIGS. 2 to 5) as the interference signal cutoffcircuit 10 used in the wireless communication apparatus according to thefirst embodiment described above.

<The Sixth Embodiment>

FIG. 11 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the sixth embodimentof the present invention.

In the wireless communication apparatus according to the sixthembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.11, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between an external antennaterminal 7 and antenna 1 is interposed between antenna 1 and duplexer 4.Interference signal cutoff circuits 10 and 12 for cutting off electricwaves having interference frequencies of Δf=|frx±ftx| are interposedbetween antenna 1 and active antenna changer switch 3 and between activeantenna changer switch 3 and duplexer 4, respectively.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from interferencesignal cutoff circuit 12 between the signal path to interference signalcutoff circuit 10 and external antenna terminal 7.

Duplexer 4 outputs the high frequency reception output signal frominterference signal cutoff circuit 12 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to interferencesignal cutoff circuit 12.

Unless a wireless communication apparatus is provided with theseinterference signal cutoff circuits 10 and 12, the transmission wave andinterference waves of interference frequencies Δf are modulated inactive antenna changer switch 3 to generate interference waves havingthe same frequency as the reception frequency frx, causing degradationof reception characteristics. In the wireless equipment of the sixthembodiment of the present invention, provision of interference signalcutoff circuits 10 and 12 makes it possible to prevent such degradationof reception characteristics.

The interference signal cutoff circuits 10 and 12 may use the samecircuit configurations(see FIGS. 2 to 5) as the interference signalcutoff circuit 10 used in the wireless communication apparatus accordingto the first embodiment described above.

<The Seventh Embodiment>

As has been described heretofore, according to the wirelesscommunication apparatus according to the first to sixth embodiments, itis possible to prevent degradation of reception characteristics bycutting off interference waves.

However, in the wireless communication apparatus according to the firstto sixth embodiments described above, there are cases where sufficientamounts of attenuation cannot be obtained at frequencies at which cutoffis wanted. Therefore, the wireless equipment according to the seventhembodiment of the present invention is designed so that frequencies atwhich cutoff is wanted can be attenuated intensively, in a simplemanner.

FIG. 12 is a block diagram showing a schematic configuration of awireless communication apparatus according to the seventh embodiment ofthe present invention.

In the wireless communication apparatus according to the seventhembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.12, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between an external antennaterminal 7 and antenna 1 is interposed between antenna 1 and duplexer 4.A trap circuit 2 for cutting off electric waves having interferencefrequencies of Δf=|frx±ftx| is interposed between antenna 1 and activeantenna changer switch 3.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from duplexer 4between the signal path to trap circuit 2 and external antenna terminal7.

Further, duplexer 4 outputs the high frequency reception output signalfrom active antenna changer switch 3 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to active antennachanger switch 3.

Unless a wireless communication apparatus is provided with this trapcircuit 2, the transmission wave and interference waves of interferencefrequencies Δf are modulated in active antenna changer switch 3 togenerate interference waves having the same frequency as the receptionfrequency frx, causing degradation of reception characteristics. In thewireless equipment of the seventh embodiment of the present invention,provision of trap circuit 2 makes it possible to intensively cut offsignals of interference waves of desired frequencies Δf, hence preventdegradation of reception characteristics in an efficient manner.

[Trap Circuit]

FIGS. 13 and 14 show circuit examples of the above-mentioned trapcircuit 2.

The trap circuit 2 shown in FIG. 13 is made up of a capacitor C4 and aninductor L3 arranged in parallel and is interposed in series in the maincircuit. The capacitor C4 and inductor L3 of this trap circuit 2 causeresonance at the cutoff frequency so as to intensively cut offinterference waves around this frequency band.

The trap circuit 2 shown in FIG. 14 is made up of a capacitor C5 and aninductor L4 arranged in series and is inserted in parallel with the maincircuit. The capacitor C5 and inductor L4 of this trap circuit 2 causeresonance at the cutoff frequency so as to intensively cut offinterference waves around this frequency band.

The characteristics of trap circuit 2 used in the wireless communicationapparatus according to the seventh embodiment will be examined based onthe simulation result shown in FIG. 6 already described.

In FIG. 6, ‘Trap’ indicated by the broken line represents the trapcircuit 2 used in the wireless communication apparatus of the seventhembodiment.

Here, it is assumed that, for example, reception frequency frx=800 MHz,transmission frequency ftx=600 MHz and Δf=200 MHz. It is clearlyunderstood from the simulation result shown in FIG. 6 that insertion oftrap circuit 2 attenuates Δf by about 19 dB and that improved cutoffcharacteristics are obtained compared to the wireless communicationapparatus according to the first to sixth embodiments describedheretofore. In this case, the loss in the pass band range is about 2.5dB at ftx and about 1.5 dB at frx.

<The Eighth Embodiment>

As described above, according to the wireless communication apparatusaccording to the seventh embodiment, it is possible to achieve largeattenuation at a frequency at which cutoff is wanted.

However, in the wireless communication apparatus according to theseventh embodiment described above, there is a concern that more than alittle attenuation might occur in the transmission/reception frequencyranges. Therefore, the wireless communication apparatus according to theeighth embodiment of the present invention is configured so that noattenuation will occur in the transmission/reception frequency ranges.

FIG. 15 is a block diagram showing a schematic configuration of awireless communication apparatus according to the eighth embodiment ofthe present invention.

In the wireless communication apparatus according to the eighthembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.15, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between an external antennaterminal 7 and antenna 1 is interposed between antenna 1 and duplexer 4.A bandpass filter 9 for cutting off electric waves having interferencefrequencies of Δf=frx±ftx| is interposed between antenna land activeantenna changer switch 3.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from duplexer 4between the signal path to bandpass filter 9 and external antennaterminal 7.

Duplexer 4 outputs the high frequency reception output signal fromactive antenna changer switch 3 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to active antennachanger switch 3.

Bandpass filter 9 is designed so that it makes transmission frequencyftx and reception frequency frx with minimum losses and that it cuts offelectromagnetic waves at interference frequencies of Δf=|frx±ftx|.

Unless a wireless communication apparatus is provided with this bandpassfilter 9, the transmission wave and interference waves of interferencefrequencies Δf are modulated in active antenna changer switch 3 togenerate interference waves having the same frequency as the receptionfrequency frx, causing degradation of reception characteristics. In thewireless equipment of the eighth embodiment of the present invention,provision of bandpass filter 9 makes it possible to prevent suchdegradation of reception characteristics. Further, since transmissionlosses therethrough at the reception frequency frx and at thetransmission frequency ftx are markedly small, degradation of receptioncharacteristics can be prevented further efficiently.

[Bandpass Filter]

As a circuit example of the aforementioned bandpass filter 9, thecircuit configuration of a bandpass filter 9 used for Δf=|frx−ftx| isshown in FIG. 16.

The bandpass filter 9 shown in FIG. 16 is composed of an inductor L1, acapacitor C1 and a capacitor C2. Inductor L1 and capacitor C1 areadapted to cause series resonance at around Δf while inductor L1 andcapacitor C2 are adapted to cause parallel resonance at around frx andftx. The capacitance of capacitor C1 and capacitor C2 are set so thatcapacitor C1>capacitor C2, capacitor C2 presents a high impedance ataround Δf and capacitor C1 presents low impedances at around frx andftx.

Thus, arrangement of bandpass filter 9 in parallel with the main circuitprovides a function similar to the way the aforementioned trap circuit 2functions, at around Δf and permits frequencies at around frx and ftx topass therethrough with markedly minimized loss.

Next, as a circuit example of the bandpass filter 9, a circuitconfiguration of a bandpass filter 9 used for Δf=|frx+ftx| is shown inFIG. 17.

The bandpass filter 9 shown in FIG. 17 is composed of inductors L9 andL10 and a capacitor C12. Inductor L9 and capacitor C12 are adapted tocause series resonance at around Δf while inductor L10 and capacitor C12are adapted to cause parallel resonance at around frx and ftx. Theinductance of inductor L9 and inductor L10 are set so that inductorL10>inductor L9, inductor L10 presents a high impedance at around Δf andinductor L10 presents low impedances at around frx and ftx.

Thus, arrangement of bandpass filter 9 in parallel with the main circuitprovides a function similar to the way the aforementioned trap circuit 2functions, at around Δf and permits frequencies at around frx and ftx topass therethrough with markedly minimized loss.

Based on the simulation result shown in FIG. 6 already referred to, thecharacteristics of the bandpass filter 9 used in the wirelesscommunication apparatus according to the eighth embodiment will beexamined.

In FIG. 6, ‘Trap’ indicated by the solid line represents the bandpassfilter 9 used in the wireless communication apparatus of the eighthembodiment.

Here, it is assumed that, for example, reception frequency frx=800 MHz,transmission frequency ftx=600 MHz and Δf=200 MHz. It is clearlyunderstood from the simulation result shown in FIG. 6 that insertion ofbandpass filter 9 attenuates Δf by about 19 dB. In this case, the lossin the pass band range is about 1.0 dB at ftx and about 0.8 dB at frx,which means that the characteristics of transmission are improvedcompared to the above wireless communication apparatus according to theseventh embodiment.

FIG. 18 is a chart for illustrating an experimental result ofimprovement in error rate for verifying the effect of the wirelesscommunication in accordance with the eighth embodiment of the presentinvention.

It is clearly understood from FIG. 18 that use of bandpass filter 9 willimprove the error rate by about 15 dB in terms of input level comparedto the case where no bandpass filter 9 is used.

<The Ninth Embodiment>

FIG. 19 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the ninth embodimentof the present invention.

In the wireless communication apparatus according to the ninthembodiment of the present invention, the receiving antenna andtransmitting antenna are integrated into one structure, as shown in FIG.19, forming a transmitting and receiving antenna 1 and the signaltransmission path is branched by a duplexer (DUP) 4 into two pathstoward a receiver 5 and toward a transmitter 6. Further, an activeantenna changer switch 3 for switching between an external antennaterminal 7 and antenna 1 is interposed between antenna 1 and duplexer 4.

This active antenna changer switch 3 performs switching of the highfrequency transmission/reception input/output signals from duplexer 4between the signal path to antenna 1 and external antenna terminal 7.

Duplexer 4 outputs the high frequency reception output signal fromactive antenna changer switch 3 to receiver 5 and outputs the highfrequency transmission input signal from transmitter 6 to active antennachanger switch 3.

Further, the length l of the transmission path, designated at 8, betweenactive antenna changer switch 3 and duplexer 4, may be adjusted so as toreduce the amount of infiltration of electric waves of interferencefrequencies of Δf=|frx±ftx| at the input terminal of receiver 5.

FIG. 20 is a chart for illustrating an experimental result ofimprovement in error rate for verifying the effect of the wirelesscommunication in accordance with the ninth embodiment of the presentinvention.

It is clearly understood from FIG. 20 that adjustment to the length oftransmission path 8 will improve the error rate by about 8 dB in termsof input level compared to the case where no adjustment is made to thelength of transmission path 8.

<The Tenth Embodiment>

FIG. 21 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the tenth embodimentof the present invention.

The wireless communication apparatus according to the tenth embodimentof the present invention includes a first antenna portion 13 and asecond antenna portion 14, and the signal transmission path is branchedby a duplexer (DUP) 4 into two paths toward a receiver 5 and toward atransmitter 6, as shown in FIG. 21. Further, a trap circuit 16 isinterposed between first antenna portion. 13 and second antenna portion14.

This duplexer 4 outputs the high frequency reception output signal fromfirst antenna portion 13 to receiver 5 and outputs the high frequencytransmission input signal from transmitter 6 to first antenna portion13.

First antenna portion 13 and second antenna portion 14 are adapted tooperate as one antenna structure. Here, second antenna portion 14 may beomitted.

Trap circuit 16 is set so as to present a low impedance to electricwaves of interference frequency of Δf=|frx−ftx|. When the wavelength ofthe electric waves of Δf is compared to the wavelengths of electricwaves frx and ftx, the wavelength of the electric waves of Δf isobviously long. Therefore, the entire antenna, which is manufactured forfrx and ftx, presents a low impedance at the frequency of Δf, so thegain of the antenna becomes markedly small. As a result, the power ofreceived interference waves becomes markedly low.

[Trap Circuit]

FIG. 22 shows a circuit example of the aforementioned trap circuit 16.

The trap circuit 16 shown in FIG. 22 is made up of a capacitor C6 and aninductor L5 arranged in series and inserted in parallel with the maincircuit. In this trap circuit 16, inductor L5 and capacitor C6 causeseries resonance, presenting zero impedance at the interferencefrequency of Δf. Accordingly, the antenna will not receive any waves atthe interference frequency of Δf.

<The Eleventh Embodiment>

As described above, according to the wireless communication apparatus ofthe tenth embodiment, the power of the received interference waves canbe weakened so as to prevent degradation of reception characteristics.

However, in some cases with the wireless communication apparatusaccording to the above tenth embodiment, provision of trap circuit 16may change the antenna characteristics of transmission/receptionfrequencies, causing difficulties in antenna designing.

With the wireless equipment according to the tenth embodiment of thepresent invention, if the antenna characteristics oftransmission/reception frequencies can be made unchanged, antennadesigning can be simplified.

FIG. 23 is a block diagram showing a schematic configuration of awireless communication apparatus in accordance with the eleventhembodiment of the present invention.

The wireless communication apparatus according to the eleventhembodiment of the present invention includes a first antenna portion 13and a second antenna portion 14, and the signal transmission path isbranched by a duplexer (DUP) 4 into two paths toward a receiver 5 andtoward a transmitter 6, as shown in FIG. 23. Further, a bandpass filter17 is interposed between first antenna portion 13 and second antennaportion 14.

This duplexer 4 outputs the high frequency reception output signal fromfirst antenna portion 13 to receiver 5 and outputs the high frequencytransmission input signal from transmitter 6 to first antenna portion13.

First antenna portion 13 and second antenna portion 14 are adapted tooperate as one antenna structure. Here, second antenna portion 14 may beomitted.

Bandpass filter 17 is set so as to present high impedances at thetransmission frequency ftx and at the reception frequency frx andpresent a low impedance to electric waves of interference frequency ofΔf=|frx−ftx|. Thus, the impedance of bandpass filter 17 is high at thetransmission frequency ftx and at the reception frequency frx, so thatthe antenna characteristics can be kept unchanged.

[Bandpass Filter]

FIG. 24 shows a circuit example of the aforementioned bandpass filter17.

The bandpass filter 17 shown in FIG. 24 is composed of an inductor L6, acapacitor C7 and a capacitor C8. Inductor L6 and capacitor C7 areadapted to cause series resonance so as to present zero impedance at theinterference frequency Δf.

Accordingly, the antenna will not receive any waves at the interferencefrequency of Δf. The capacitance of capacitor C7 is set to be muchgreater than that of capacitor C8, so that the impedance of capacitor C7becomes low at the transmission frequency ftx and at the receptionfrequency frx. Inductor L6 and capacitor C8 are adapted to causeparallel resonance at the transmission frequency ftx and the receptionfrequency frx, so the impedance becomes infinitely large.

If the thus specified-band filter 17 is attached as a part of theantenna, it is not perceived as a load by the antenna, so that therewill be no influence on the antenna characteristics.

The wireless communication apparatus according to the present inventiondescribed heretofore can exhibit maximum realization in improvement ofthe reception characteristics especially when it is applied to IMT2000(International Mobile Telecommunication 2000) where the receptionfrequency band is set from 2110 to 2170 MHz and the transmissionfrequency band is set from 1920 to 1980 MHz. Illustratively, thedifferential frequency when the above transmission/reception frequencybands are designated is 190 MHz. Since the television frequency bandexists in the 190 MHz band, there has been a concern of high powerinterference waves occurring. The wireless communication apparatus ofthe present invention will not be affected by such interference wavesand can be improved in reception characteristics.

INDUSTRIAL APPLICABILITY

As has been described heretofore, the wireless communication apparatusof the present invention is useful for wireless communication systemssuch as cellular phones, automobile phones and the like, and inparticular, is suitable for cutting of interference signals which ariseand are dependent on the transmission frequency and reception frequencywhen the reception frequency and the transmission frequency are usedsimultaneously for communications.

1. A wireless communication apparatus which establishes communicationusing reception and transmission frequencies simultaneously,characterized in that an interference signal cutoff circuit for cuttinginterference signals having frequencies approximately equal to theabsolute value of the sum or difference of the reception andtransmission frequencies is interposed between the input terminal to areceiver and an antenna.
 2. A wireless communication apparatus whichestablishes communication using reception and transmission frequenciessimultaneously characterized in that an interference signal cutoffcircuit for cutting interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies is interposed between theinput terminals to a transmitter and a receiver and an antenna.
 3. Awireless communication apparatus which establishes communication usingreception and transmission frequencies simultaneously and has a switchmade up of active elements interposed between the input terminal to areceiver and an antenna, characterized in that an interference signalcutoff circuit for cutting interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies is interposed between theswitch and the antenna.
 4. A wireless communication apparatus whichestablishes communication using reception and transmission frequenciessimultaneously and has a switch made up of active elements interposedbetween the input terminal to a receiver and an antenna, characterizedin that an interference signal cutoff circuit for cutting interferencesignals having frequencies approximately equal to the absolute value ofthe sum or difference of the reception and transmission frequencies isinterposed between the switch and the input terminal to the receiver. 5.A wireless communication apparatus which establishes communication usingreception and transmission frequencies simultaneously and has a switchmade up of active elements interposed between the input terminal to areceiver and an antenna, characterized in that interference signalcutoff circuits for cutting interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies are interposed between theantenna and the switch and between the switch and the input terminal tothe receiver.
 6. The wireless communication apparatus according to anyone of claims 1, 2 and 3 to 5, wherein the interference signal cutoffcircuit is composed of a trap circuit having a resonance frequencyapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies.
 7. The wirelesscommunication apparatus according to any one of claims 1, 2 and 3 to 5,wherein the interference signal cutoff circuit is composed of a bandpassfilter having pass bands including the communication frequency and thetransmission frequency and having an attenuation band around thefrequency approximately equal to the absolute value of the sum ordifference of the reception and transmission frequencies.
 8. A wirelesscommunication apparatus which establishes communication using receptionand transmission frequencies simultaneously and has a switch made up ofactive elements interposed between the input terminal to a receiver andan antenna, characterized in that an impedance adjusting circuit foradjusting the impedance to interference signals having frequenciesapproximately equal to the absolute value of the sum or difference ofthe reception and transmission frequencies is interposed between theswitch and the input terminal to the receiver.
 9. A wirelesscommunication apparatus which establishes communication using receptionand transmission frequencies simultaneously, characterized in that acircuit presenting a low impedance to interference signals havingfrequencies approximately equal to the absolute value of the sum ordifference of the reception and transmission frequencies is provided asa part of an antenna.
 10. A wireless communication apparatus whichestablishes communication using reception and transmission frequenciessimultaneously, characterized in that a circuit which presents highimpedances at the reception frequency and the transmission frequency andwhich presents a low impedance to interference signals havingfrequencies approximately equal to the absolute value of the sum ordifference of the reception and transmission frequencies is provided asa part of an antenna.
 11. The wireless communication apparatus accordingto any one of claims 1, 2 and 3 to 5, wherein the reception frequencyfalls within the range from 2110 Hz to 2170 Hz and the transmissionfrequency falls within the range from 1920 Hz to 1980 Hz.